Telecommunications networks pass user data such as voice and data traffic between a source device and a destination device. Often data transmitted from the source device to the destination device is in the form of Internet Protocol (IP) data packets, although data to be transmitted may take a wide variety of other forms.
Many telecommunications networks, including mobile telecommunications networks, employ a tunnelling protocol for transmission of user data between network elements such as the source and destination devices. In tunnelling protocols user data is encapsulated within other data that is being transmitted from one network element to another.
Satellite communications systems can be used to provide both voice and data services to remote locations. In transmitting user data such as voice and data signals, a satellite transmission terminal manipulates the user data to adapt or optimise it to suit the characteristics of the satellite service being used to transmit the user data. For example, voice traffic may be compressed, whilst data packets may be manipulated to make the best possible use of space segment data frames provided by the satellite service.
Mobile telecommunications services can be provided using satellite systems for the backhaul connection. Indeed, in principle any network link between two network elements could be implemented using a satellite connection. An example of this principle is illustrated in FIG. 1, which shows, in schematic form, part of a telecommunications system which uses a satellite connection. In the system illustrated generally at 10 in FIG. 1, a Radio Network Controller (RNC) 12 of a mobile telecommunications network transmits user data, such as voice and data traffic, to a satellite transmission terminal 14. The satellite transmission terminal 14 transmits the voice and data traffic, via a satellite link 16, to a satellite ground station 18. The satellite ground station 18 transmits the received voice and data traffic to further network elements of the telecommunications network such as a serving GPRS support node (SGSN) 20, which receives the data traffic and a Mobile Switching Centre (MSC) 22, which receives the voice traffic.
There are disadvantages in using a satellite system, such as high latency, low bandwidth availability and high costs. The optimisation capabilities of satellite terminals discussed above are designed to offset some of these disadvantages.
However, in most cases the optimisation capabilities of satellite terminals function only on basic voice and data packets. If data presented to the satellite transmission terminal is in a tunnelled format in which the user data (e.g. voice and data traffic) is carried as a payload within a tunnel of other IP data packets to be transmitted, the optimisation capabilities of the satellite transmission terminal operate only on the outer tunnel (i.e. the “other” IP data packets to be transmitted) without affecting the payload of user data.
Additionally or alternatively, traffic within a telecommunications network, whether or not the telecommunications network employs a satellite link, may be handled with different quality of service profiles, and thus treated differently within the network depending on these profiles. However, quality of service based treatments of traffic can only operate on basic voice and data packets, and so such treatment is not effective when the traffic to be transmitted is tunnelled or embedded within other traffic to be transmitted.